It is well known to carry out checkings, such as "non destructive" checkings, of mechanical parts in order to check their structural quality after machining in machine tools, such checkings being quite important in mass production in order to respond to very strict requirements relating to the reliability and safety of components subject to stresses.
In the specific case of bearing rollers it is important to check the rolling surfaces in order to detect the presence of cracks, flaws or other surface defects.
These checkings can be performed by non contacting probes, such as optical probes or eddy current probes, that detect the possible presence of determined defects on the concerned surface through mutual rotational movements between the probe and the part. In order to check all the part surface, said rotational movements are combined with mutual translation movements, thus permitting the probe to fully scan the surface. The combined mutual movements can be obtained in different ways, for example by making the parts translate and the probe rotate about the roller axis, or by making the parts rotate about their axis and the probe perform translation movements substantially parallel to the surface to be checked, etc.
Since, to a certain extent, the surface defects of the parts arise with a stochastic distribution, a sampling inspection is not sufficient, but it is necessary to inspect all the parts. For this purpose the rollers, for example coming out of a machine tool after grinding or superfinishing machining, can be displaced and guided, arranged as a row, by a conveyor towards the inspection probes, that scan the rolling surfaces.
The inspection of conical rollers is difficult due to problems for the mutual arrangement of the parts and the probes, deriving from the necessity of maintaining, during the mutual rotation and translation movements, a substantially constant distance between each probe and the surface to be checked.
U.S. Pat. No. 3,787,983, to which is referred the preamble of claim 1, discloses an apparatus for the surface inspection of conical rollers, in which the rollers are located one at a time at an inspection station, where suitable rotating supports cause their axial rotation, while stop means prevent translation displacements and an inspection probe can oscillate along a longitudinal direction. The arrangement of the rotating supports is such that the external surface of the rotating part presents, in a longitudinal section, a line parallel to the longitudinal direction, whereby a constant distance can be maintained between the probe and the surface and the probe can scan the surface.
The apparatus according to the above mentioned U.S. patent comprises a rather complex and delicate device for positioning and displacing the parts and the probe, with several elements that have to perform coordinated operations for feeding the parts, loading them between the rotating supports, displacing the parts against the stop means, closing the rotating supports against the parts, rotating the supports and simultaneously oscillating the probe, releasing the parts and ejecting them. This device must be separately actuated for the inspection of each part and therefore the operation of the apparatus is rather slow and complex. Moreover, the above mentioned steps can alter the surface state of the parts, due to wear in the rolling surface and in the surface contacting the stop means, also in view of the considerable forces applied to the part being inspected.
It is also known to transport objects by means of nonparallel rollers supporting the objects and rotating about adjacent axes.
U.S. Pat. No. 3,260,390 shows a conveyor for transporting elongate objects, such as pipes, and comprising couples of rolls (e.g. "small-size pneumatic airplane wheels") aligned along two skew axes.
The conveyor according to the U.S. patent cannot be employed for translating a row of little rollers, and, anyhow, could not guarantee a precise location of the surfaces of the rollers during their feed.